Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share Reconciliation [Abstract]
Net Income (Loss) Attributable to Parent	$ 18,871	$ 25,820
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	217	309
Net earnings available to common shareholders	$ 18,654	$ 25,511
Weighted-average outstanding shares of common stock - basic	47,873,007	47,463,231
Dilutive effect of equity incentive plans	123,305	242,920
Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares	710,405	1,059,880
Weighted-average outstanding shares of common stock - diluted	48,706,717	48,766,031
Basic	$ 0.39	$ 0.54
Diluted	$ 0.38	$ 0.52
Share options excluded from the computation of diluted earnings per share	0